This invention relates to liquid purification in water valves involving a screening device inserted into the open end of a pipe or inlet channel. The screening device is positioned such that water flowing through the valve inlet channel must pass through the screen to prevent particles in the water larger than the screen openings from passing through the channel along with the water.
Contamination, especially in the form of particulate matter, can impair the operation of water valves. Contamination can take many forms including sand particles, mineral particles, organic particles, mineral deposits, or other impurities. The basic structure of a pilot actuated water valve provides many opportunities for contamination to impair valve operation. There are small passages through which water must pass such as a bleed passage and a pilot passage. There are also close fitting parts that must move or seal such as the fitting between the pilot valve outlet extension and the outlet, and the seal between the diaphragm and valving surface.
A water valve impairment can also take many forms including the following: a complete bleed passage obstruction causing catastrophic valve failure; a partial bleed passage obstruction slowing valve closing thereby wasting water; an obstruction between the outlet and the pilot valve outlet extension causing valve failure; a partial obstruction between the outlet and the pilot valve outlet extension causing slowed or incomplete valve closing; an obstruction between a guide tube and armature that causes valve failure; or a partial obstruction between the guide tube and armature that interferes with pilot valve operation.
An impaired water valve often increases water consumption through incomplete or slow closing. When an inlet water valve used in a household appliance is impaired but still functional, it may be difficult for the appliance operator to recognize the impairment because the water valve will leak to a holding tank or to a drain which may not be visible to the appliance operator. If the water valve is impaired by closing more slowly than designed, then water levels may be higher than desired or water volume may be greater than desired or the water valve may direct some water directly into an open drain. Unnecessary water consumption is not desirable, particularly when the water wasted is hot water. Wasting of even small amounts of hot water increases energy consumption.
Because of the destructive effects that contaminate particles may have on a water valve, a screening device is placed at the inlet to the water valve. The presence of an inlet screen prevents contaminate particles larger than a specified diameter from entering into the main valve, thus reducing the chance of valve failure as the result of an obstruction from a contaminate particle. Some prior art water valve inlet screens 22P, such as shown in FIG. 1, have been manufactured from a woven wire cloth 56P, such as that produced by Newark Wire Cloth Co., Newark, N.J., of forty (40) mesh, i.e., mesh with width of openings of 0.016 inches (0.041 cm) to produce an open area percentage of 41%, and made with 0.009 inch (0.022 cm) diameter wire. However, as contaminate particles collect on the screen, the screen openings 57P become blocked by large particles resting on the screen or lodged in the screen openings 57P. When enough of the screen openings become blocked, the free flow of water into the valve is impaired and valve failure results. An example of a water valve with a wire inlet screen is disclosed in U.S. Pat. No. 5,269,333 issued to Richmond.
For the foregoing reasons, there is a need to reduce clogging in the water valve inlet filter to reduce the probability of substantial blockage of the filter causing the valve to fail.